Firefighters often use radios within buildings to communicate with one another and with other firefighters outside. These radios typically use line-of-sight transceivers that may not adequately reach all areas of the building. In addition, tint coating on building glass in many modern buildings attenuates or blocks RF signals and thereby prevents reliable communication between firefighters inside and outside the building. Similar problems may be encountered by police and other emergency personnel.
To address these problems, a distributed antenna system (DAS) can be installed in a building. A DAS can include a plurality of antennas that are distributed within a building, which can increase radio coverage for first responders like firefighters, policemen, and emergency medical technicians (EMTs). A DAS used by first responders may be referred to as a public safety DAS or Emergency Responder Radio Communication System (ERRCS). Moreover, a DAS can also be employed for other uses, including extending cellular coverage inside a building. Convention centers, for instance, may employ a DAS for large conventions to enable convention goers to maintain cellular connectivity that would be impossible without the DAS, due to the heavy load on limited cellular resources.
Referring to FIG. 1, an example prior art scenario 100 is shown in which a DAS can be implemented in a building 110. The building 110 includes a donor antenna 102 on the roof. This donor antenna 102 can communicate with external antennas, such as first responder antennas (not shown) or cellular network radio macro towers 108. The donor antenna could also be located on another portion of the building other than the roof, such as the side of the building.
The donor antenna 102 can receive signals from the first responder antennas or cellular network radio macro towers 108. These signals can be transmitted along a wire such as a coaxial cable (“coax”) to a bi-directional amplifier (BDA) 130 within the building 110. The donor antenna 102 can also receive signals to be transmitted from the BDA 130 over the coax. The BDA 130 can act as a repeater that amplifies both received and transmitted signals received from or transmitted to the donor antenna 102.
The BDA 130 can supply and receive signals from additional cabling shown in the building 110. This cabling communicates with indoor antennas 160 through coax cables 150 or fiberoptic cables (not shown). The cables connect to the indoor antennas 160 and to the BDA 130 via antenna couplers 140, such as taps or splitters. The indoor antennas 160 can be provided on some or all levels of the building 110.